Recovery and fractionation of light hydrocarbons



Aug. 3, 1943.

ABSORPTION OIL III: ABfiORBER 2'6 DRY GAS :1: FRACTIONATING AU5ORBER UMN 0 ABSORPTION OIL I T Hi-IA ER 78 HEATER HYDRO ARBON g I GASES, ETC. (1

Z2 Z r 7 5'2 To FRACTIO ATINGY EQUIPMENT INVENTCR DAVID G. BRANDT D. G. BRANDT 2,325,588 RECOVERY AND FRACTIONATION OF LIGHT HYDROCARBONS Filed Dec. 27, 1940 Y ATTORNEY the high pressure necessary would have practical ly no cooling 'efiect because the temperature is about the same as the critical temperature or I ethane, Where the heat of. vaporization is sub stantially zero. It has been found tl 'atiira refluir containing twoormore hydrocarbonsisusedit is possible, because of the partial pressure effects from the effect of the critical conditions of the single 1 hydrocarbon. The present ihvc'ri'tion ther re s an' m e emii t e ecov y an ficat on.o -su hc rb m tu s. wh ch is -particularlyl adapted ior therecovery. of C3 carbon mixturesj The primary ob ject oi-' the;present inventionis of-light-hydrocarbons and the high pre'ssurefracgate the low molecularvweight;constituents orthe yp of h .Gahydrocarbons. Q 5' .Q Knother 1 object'zof the invention is is. process which i is particularly adapted for the ;-recovery of C3 hydrocarbons-from.mixturescontaining' C2. hydrocarbons .The I features er. the present; invention are substantially disclosed in pending application Serial No. 225,079, but other objects andfa'dva'ntages will be apparent mm the following detailed description of the invention taken in' connection with the accompanying draw- .ingi-inwhichz; r

.The singlefigure is diagram of. an apparatus particularly 'a'dapte'd vent invention. I

. 'Referring to the p mixture to be treatedfand which riia'y derived from anyso u'rceSuch'as'natural gas,cde petro versi-onoperations, and which inay com'prise drocarbions boiling in the :gasoline'rangejas well asboth lowera'nd higher boili-nghydrocarbons;is introduced into th'e apparatus through a e "2 "after-being cooled to aeertam'excem su'mcient to condense ally of the: readily condensabl' es uents;v The uncondensedgase'ous hydra in 1 contact with molejcularwiglrtfg ases being dischargedfrom'the top of the absorber"! =througl'ia "pressure valve 14 may range "fro abate 1 p "ibsfpr square jch, "dependi-nguponthe m rsh- 1-bemg rccesse to provide .Vfor f. carrying. out the improvements of the presl,

erawinailtnehydrocarbon leum 'or gfrom varioustypes. orchyarddar'tmeenint'oithe lowerportiono'f an absorber'd, preferably c the r-aiiparatus' -ents-which-maycornpri'seess ntiallyCza'nd lower 'of the two-or more hydrocarbons, toget away tus through the line 6 may be obtained from any source and comprise any suitable cil adapted to perform the absorption referred to. 'tion medium may be adistillate produced at a later stage in the process fromthe hydrocarbon mixture introduced through the line 2 such as a distillate of higher boiling point than gasoline, andsubs t'antially free of light constituents.

The rich absorption oil reaching the bo'ttoin of the'abS Qrber 4 is mixed directly with theliquid hydrocarbons introduced through the line 2, and. V the resulting iniirtiir'is Withdrawn through a line T5 and forced by means of a pump therein at a.

prss'ureo'i rrsm 500 to 650 lbs. persquare" ch'thrf'gh'a heater l8 and then into a-frac- Y tionaftirig column preferably at an intermediate point as shown. The fractionating column 20 is used primarily to carry out a rectifying opemtion adaptedto separate C2 and any lower molecular weight constituents'rfromthe-hydro- V product substantial-ly free-of such constituents hydrocarbonsiand to ef ect separation of C2, and and which will therefore be morereadily handled lower molecularweig-htconstituents-from hydroto'provide; an improved process for the; recovery suitable temperature such'as of frbm25lto-3l0 V is -recti-fied the column '23 atprcssures' approximately withint-he range referred to. above.

ticnation oigthesame.to more effectively "Se In carrying out the fractionation in'cclurnitifl the bottom of the-column i's heatedby-nieans of v ahea'ter 2.-2'-or byg'other 'suitablereb'oiler, to maintainthenecessar y temperature,..'such as apprenmately 375 F.Ij lhe stocksupplied to the use 2,

a conventional eleyational if hot enough may be used inheaters l8 'and22 to do the necessar'y heati'zig, 'At'the same time' t'he top'of thec'olurnn -20'i's preferably cooled topro- V duce-a refluxing action, as for example, by means of a cooling'coil 24 Other means for supplying rrefiux to the column 20 may be provided'instead 1 make acleanbut between the 'Ca and-the Gi' hy- ;drocarbons because @the scooling' and refluxing at the high pressures employed s'ee m to-have little influence in retaining sufiicientUz-for reflux 5pm 7 poses, forthereasons'pointed outabove; There- -;f ore, the overhead vapsrrraction produced by I the column 40,. in accordance with the-present Drocess,comprises"Gz hydrocarbon as wanes some 7 {C3 hydrocarbon, and possibly-"some isobuta-neor got-her C4...This mixture is e'oaduetea from the :column 20 throughaiva'poriin rb ns I joflthe mixture introduced into the -=absorber and notabsorbed. in t'the' iiqu amasatuents; pass commie amen; 'irhe'pressre n absorber,

charges ists an 1-1 iii-to an absorber .28 whi'ch' is operated "at pressure only --s1ighft1y lower than that 'm'ai-ntamed in the col umna-o. In the-apparatosas shown; the pressure intlie absorb'e'r zs "will e slightly lower top'ro vide for 'va or now from thecolum'n iii. The ab? sorptionmedium used *n'ni'e abserber re my be *ofthezairietYp a i "the absorber introduced into 'the top the abS'Olf of t e absorber" ore m 'hlii'l matinee "in the bottom "roa'ghf-a iineee, which disn-e l fiflead'ing *to the e mmn i 20. a swa be 'pf'o'videdin thelin the absorber 28 be-elevated as shown 'g avityjfiew tammnfzo. ,"Thea'bso pussi s V {Theabsorption-oil"introduced'intothe'ai bai 7'5 'rateaaatenrseratareaaafitea tbebsbitsabstan- The absorpthe Valve d extension :or

- hydrocarbonrnixture recovered: inrth who 11=1tia11y f t a andh a erhrdmarh hs 1 n- 1 tam d i the ap sat-s re m i 't e z in .25

1 11116 absorber 11 8 hereiqre perfiq 'ms a very im- 1 port u iohlin co r hsathecaa dhis e h ro ar n which w ldl-o erwi eh 01 t --and -11 '1 1 in supp ina t hac to he ra io stms' rbo l mn 1120 where it is oflvalue injthe rectiijcationpi the ajp ssur w ive nt o l ine asflsh wn and ,thelower portion of a bsorber 31 the hve 1; o er cqnt tu nts -1L m 1 111 he 1 1 1 2 1 1 und r the onditionsfie- 1 .{scribed above g-will 1 1": owe mol ul r we ht commune 1 1 c e t r hi h mper u e is m i ta d n a t dc pressu e: i to a fie i ablen h ompl t lvi ee f 1any1lC V p v 1 w w p 1 i nto said,scc n abso ptioh t ie m inta I bottomof thecolurnn 20 101: this 1pu'rpose -'This mh ureliswithdrawnniromwthecolumn through i 1 e n 32, and p edhx mesn 0 'apu h the ein a i '1 o1'1 he1 ir cti at hzg ipment:wh tha 1 1-n ztu1 ev be ra ti hat dto pr duce; t e 1 J1 si indivi a e ha1'suc 11 dr1examp 11 njd 1 C 1 tra on-s, ,a a as ne; i n qe o l a other h he b i lns d s illa .in;1a rd n 1 {with t compo t o o a he ri inal mixt e-1 m tr uce o appa us t rou h; th hu z. 1

uc im oha ion'aw l b b ind 1w; reatly I -simpl fl andmuch o e Y 1 carri d Qutbe' cause of the absence oixCrandlower molecular 11 1 T w i c n s n 1 m ter al-discharce i th h theil ecfl- It w l he =no d fhrther-1 1 p 1 more 1-that1in; the; operation as describedgthepaf hydr ca ons e over with t th .us 0 11mm! pressors, 1 and :1 that nothing, but liquids are I m 1' 1'h s o -1 o 1 ld rable a commercial operation. a 1 H Itlstobeunderstpod that various modifications may be'made in the process of the presentinvention without departing from-the deflni'tionithereoi as: presented in the accompanying 1 claims. It is who Iurthe'rl understood that the gimportano 1;;

p t on o 4 s cond abso ption tower sep ate :.1 1 a sqrp oh td chi to 1 a 1a na column .at a;point 1below themid-point thereofiand recti-' 1 yins'the rwaf w m xtu e-un r flu n on it ons .pro c x v thelwohns; of va o at qthert po Ihec mn; ma ntalh hsa b t 'r *pe u n t I w m i smm n a t m pr ducesx o tqm lp fody t co thl naC h -f 1 a er on b t hi h issuhst t ly i Q fC=1:. v-

1 1 1 P .d Qca bQm ischarti s the hh t mapmd ct; o

jt ih ha h dr a bon fro the. b o -h th 1 1 c ur u.-pa ns aya o fi hqfi n disc ar ed from j he..ton1. fliet j act onat eic um landn qm 1 p smeaca l we 2 m e ula w ht hy rojcarbons but which isfsubstantially freekot higher rnolecular weightf hydrocarbons into fthe lower 1wtiong-1in intimate ,contactwithjan-qabsorption 1 medium adapted t absorb substantially allot the Ca hydrocarbon-ct the vapor fraction introduced igh pressure p :in 1 said second absorption 1 tower rates point :to11 returniQa1 hydro arbon; thereto. n

2.; Thepprocess of recovering-desirable hydro-1 1 carbon constituents iromzmixturesoi hydrocar- 'bons ucont-aining 1;:hydrocarbons normally within Ithe gasoline L range; and 1 constituents 01 lower-1 molecular; weight such as Grand C2 hydrocar 1 bOlilS,g-Whi6h 1 comprises apassingsthe hydrocarbon mixture tq; b,ejtreated int othe lower portion of fantabsorption tower inwh-ichwthe gaseous ,constituentsgare broughtvim:lntimate-contactfwith f anzabsorbingo-medlum under yconditions adapted 1 to'retain 'inqthe towerisubstantially alliof thepz 1 and? higher .imolecularrweight ehydrocarbons as 1 1 well as. some Crhydrocarbom discharging unabprocess is not limited to-the handlingloi'any'parsorbedgaseous 'hydrocarbonirom the upper part 1 of the absorption tower, passing the rich absorp tion medium and recovered hydrocarbons from 1 the base of the tower into afractio nating column 1 at aninter'mediatepoint iniwhich the hydrocarbon mixture is subjected to rectification at a high 1 may be applied tofthe treatmentot hydrocarbon l,

. mixtures to be handled in the various art's, such as in the conversion 011 hydrocarbons, the re 1 covery of hydrocarbons petroleum" and 1 other sources Having thus claimed as new is; 1 1

1. The process of recovering desirable hydrofrom naturiail gas, crude :1

1 pressure of the order of '500 lbs. per square inch and under; 'overheadrefluxing conditions, maintaining acbottom temperature in the fractionatdescribed the invention, what is carbonconstituents from mixtures of hydrocarbons containing. hydrocarbonsinormally within 1 r 1 ing the hydrocarbonm'ixture to be treated con- 1 taining said; constituents into the lower portion or an absorptionitower in which the gaseous constituents are broughtin intimatecontact with an 1 absorbingmediumwhich is introduced into the upper portion of thetcwer, eflectingthe intimate 1 l n V I n V isecond absorption column, and 1 passing the rich contact N under conditions adapted to retain in the tower substantially all of the C3 and higher the gasoline ra eas we higher minngl'con' inecolumn adaptedto'produce a bottoms prod uctcontalni'nsCa hydrocarbon butwhich is'sub V stantiallv freeot Ca hydrocarbons, passing a 1 vapor mixture comprising Ca'and lowermolecular weight hydrocarbons removed from the topsoi said fractionating column andwhich is substantially free of normally liquid hydrocarbons into with an'absorption medium, adapted to absorb substantially all of the 1C: hydrocarbon of the vapormixture introduced 'thereinto, saidsecond 1 1 1 absorption tower being'separate' from said col-- Qumn, maintaining a high'pressure in said second absorption tower substantially equal "to that mair'itainecl,in said fractionatingi column, distnar m rcr hydrocarbon from thetop or said ,termediate pointabsorbed C2 and lower molecular weight hydrocarbons from; the upper part of the absorption 1 tower, passing'the rich absorption medium andfl recovered hydrocarbons oi the hydrocarbon mix- 1 ture introduced into thetcwer from the basegot towerIinto said fractionating column at an in- 3. [In' the fractionation a "second absorption tower in intimate contact of hydrocarbon mix- -1 tures containing Ca hydrocarbon jand-hydrocar- -bon material of higher and lower molecular '31 weight in which the iractionationis carried; out 1 

